The lateral motion of the web is one of the most common problems in roll-to-roll (R2R) systems, which results in degraded product quality, waste, or even processing interruption. An industrial proportional-integral-derivative (PID) controller with fixed gain is mostly used for lateral position control. In fact, the model parameters of the web lateral dynamics such as the tension and the transport velocity of the web are seldom exact. Variations of these parameters could significantly affect the lateral web dynamics. A dynamic matrix control (DMC) strategy is adopted in the offset pivot web guide to control the lateral position of the web, which does not depend on accurate model. Simulations of the DMC controller and the PID controller was carried out with a sinusoidal disturbance in different web conditions. The results show that DMC controller performs much better than PID controller with good disturbance rejection. It is observed that the lateral position of the DMC controller is less than a half of that of the PID controller. As the web velocity decreases or the web tension increases, the lateral position becomes smaller.
At ambient substrate temperatures, NbN and AlN thin films as well as NbN/AlN/NbN sandwiches are prepared on single crystal MgO substrates, using direct current (dc) or radio frequency (RF) magnetron sputtering techniques. Excellent single crystal orientations of these structures are revealed by x-ray diffraction and transmission electron microscopy (TEM), while x-ray photoelectron spectroscope (XPS) shows that the stoichiometric composition of the NbN films is 1: 0.9 (Nb:N). Furthermore, AFM (atomic force microscope) scans indicate a root mean square (rms) roughness of 0.755 nm for AlN/NbN, and 0.83 nm for AlN, both over an area of 5 µm × 5 µm.
Aluminium nitride (AlN) is very useful as a barrier in superconductor-insulator-superconductor (SIS) device or as an insulating layer in many other applications. At ambient temperature, we deposit AlN thin films onto different substrates (such as MgO, LaAlO 3 and Si) by using radio-frequency magnetron sputtering and pure Al target. X-ray diffraction (XRD) and -scan patterns show that the films grown on MgO substrates are excellent epitaxial films with (101) orientation of a hexagonal lattice. A possible structure of the interface between the film and the substrate is suggested and discussed.
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